package pc;
/**
 * 线程之间的通信问题：生产者和消费者问题
 * 线程交替执行 A B操作同一个变量 num=0
 * A num+1
 * B num-1
 */
public class ConsumeAndProduct {
    public static void main(String[] args) {
        Data data = new Data();

        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "A").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "B").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "C").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "D").start();
    }
}
//判断等待，业务，通知
class Data {//数字，资源类
    private int num = 0;
//只要是并发编程一定会有锁。
    // +1
    public synchronized void increment() throws InterruptedException {
        // 判断等待
        while (num != 0) {
            this.wait();
        }
        num++;
        System.out.println(Thread.currentThread().getName() + "=>" + num);
        // 通知其他线程 +1 执行完毕
        this.notifyAll();
    }

    // -1
    public synchronized void decrement() throws InterruptedException {
        // 判断等待
        while (num == 0) {
            this.wait();
        }
        num--;
        System.out.println(Thread.currentThread().getName() + "=>" + num);
        // 通知其他线程 -1 执行完毕
        this.notifyAll();
    }
}
/*
执行结果：
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
A=>1
B=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
C=>1
D=>0
 */